blockdev: Don't use qerror_report() in do_drive_del()

blockdev: Don't use qerror_report() in do_drive_del()

qerror_report() is a transitional interface to help with converting
existing HMP commands to QMP.  It should not be used elsewhere.

do_drive_del() is an HMP command that won't be converted to QMP (we'll
create a new QMP command instead).  It uses both qerror_report() and
error_report().  Convert the former to the latter.

Signed-off-by: Markus Armbruster <armbru@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>